Study of the magnetic phase transition in a cyanide-bridged molecule-basedmaterial: [Mn(cyclam)][Fe(CN)(6)]center dot 3H(2)O (cyclam=1,4,8,11-tetraazacyclotetradecane)

Heat capacities of [Mn(cyclam)][Fe(CN)(6)] . 3H(2)O (cyclam = 1,4,8,11-tetr aazacyclotetradecane) under zero magnetic field in the 0.1-300 K range were studied by adiabatic calorimetry. A heat capacity anomaly corresponding to the magnetic phase transition was detected at 6.2 K. The observed entropy gain (DeltaS = 2.32R) is in good agreement with the theoretical magnetic en tropy (R In 5 x 2 = 2.3R) considering the spin multiplicity of high spin tr ivalent Mn and low spin trivalent Fe ions. Attempts have been made to inter pret the low temperature heat capacity data in terms of the spin-wave theor y. Possible magnetic interaction mechanism is discussed by comparing with t hose of related compounds. Heat capacity studies under applied magnetic fie lds indicated an anti ferromagnetic to ferromagnetic transition. A field de pendence study of magnetization at different temperatures revealed a field- induced metamagnetic transition. (C) 2001 Elsevier Science B.V. All rights reserved.